Learn all the formula and the derivations. And slowly start with the application questions.
Study Clix itself contain videos on Trignometry
https://www.studyclix.ie/resources/leaving-certificate/higher/mathematics/trigonometry
This link also has good videos relevant for LC . Its from UCD
https://www.ucd.ie/msc/leavingcertificatevideos/geometryandtrigonometry/trigonometry/
Hope this helps.